The United States launched airstrikes against the IS fighters in Iraq back in August, following the jihadists' rapid advance in the country's North. The Sunni extremist group had earlier proclaimed an Islamic caliphate on the large areas it controls in Iraq and Syria.
In September, US President Barack Obama outlined a strategy of fighting the IS and other terrorist groups in the Middle East. The plan implied the establishment of a multinational coalition to counter terrorism in the region.
Since the beginning of the week, Washington and its Arab allies have been carrying out airtrikes against the IS and other insurgents on the Syrian territory, without any formal permission from Damascus. On Friday, the UK parliament approved the participation of the British military in the airstrikes in Iraq.